Looking for a missing part on a printer I just got 2nd hand

[Confused_64]

I'm basically just looking for a parts list for this printer and can't find one. I think I got all the paperwork with the printer, but I can't find the parts list. I think I know what it's missing, but I don't know what it's called. 
It's the thing the paper feeds into in the back of the printer and you remove to remove a paper jam.  I hope someone understands what I mean. I got this second hand from a sweet older gentleman who had no clue, his wife took care of all the office stuff and she is no longer with us. He was trying so hard to find everything for me. 
I just hope I can get the part I need. Thanks in Advance if anyone knows what I'm talking about. 

[Repairatrooper · Accepted solution]

Either a jam removal door or duplex door. There will be no parts list simply due to the fact that beyond ink cartridges and power cord, typically parts are not available. You could check hppartsurfer.com, but typically you are going to have to search around Ebay or local bid sites and find either another printer you can take parts from or someone selling parts from failed machines.

[Loadace]

My advice, youtube paperjams for your model, it'll tell you during the explanation